1. Field of the Invention
The present invention relates to an image blurring correction apparatus, and in particular, to the image blurring correction apparatus for correcting (preventing) an image blurring of a camera due to vibration.
2. Description of the Related Art
For instance, as for an image blurring correction apparatus of a TV camera, there is a known one wherein a vibration-proof lens is placed to be movable within a surface perpendicular to an optical axis in an image taking optical system, and if the camera (image taking optical system thereof) is vibrated, the vibration-proof lens is driven by an actuator in a direction for counteracting the vibration so as to correct an image blurring. As for such an image blurring correction apparatus, the vibration applied to the camera is detected by a blurring detection sensor (angular speed sensor, acceleration sensor, etc.) so that a displacement amount of the vibration-proof lens for correcting the image blurring is acquired according to a blurring signal outputted from the blurring detection sensor (refer to Japanese Patent Application Publication No. 2002-229089 for instance).
The blurring signals outputted from the blurring detection sensor includes signals caused by intentional camera operation of an operator such as pan or tilt operation in addition to the signals caused by the vibration to be corrected such as a blurring caused by hand. Therefore, if the vibration-proof lens is driven merely according to the blurring signals, an image blurring correction is performed even on the pan or tilt operation. If the image blurring correction is performed on the pan or tilt operation, however, it is not desirable because the image blurring occurs after finishing the pan or tilt operation so that sense of discomfort may arise in the camera operation and image.
Thus, there is a proposal in the past as to an apparatus wherein it is automatically determined whether or not the blurring signal outputted from the blurring detection sensor is caused by the pan or tilt operation, and if determined so, the image blurring correction is stopped and the vibration-proof lens is returned to a center of a range of movement (reference position of displacement amount 0) and stopped (refer to Japanese Patent Application Publication No. 5-142614 for instance).
As for control of the vibration-proof lens on correcting the image blurring in the past cases, the blurring signal from the blurring detection sensor is filtered with an IIR filter or the like, and the vibration-proof lens is moved by rendering the result thereof as a position signal so as to correct the image blurring. On the pan or tilt operation, a filter constant is changed to return the vibration-proof lens to the reference position.
Even in the case where an image blurring correction is stopped on pan or tilt operation as described above, however, there is a problem that a phenomenon (swingback) occurs, in which an image jitters (jerks) due to operation of returning a vibration-proof lens to a position of a displacement amount 0 (reference position) as if the speed of the pan or tilt operation is instantaneously changed. The swingback does not cause so much sense of discomfort when performing the pan or tilt operation by setting a zoom on a tele-side because the images change fast. In the case where the zoom is set on a wide-side, however, there is a problem that the swingback conspicuously appears even when performing the pan or tilt operation at the same speed as when setting it on the tele-side and the sense of discomfort arises in the camera operation and image.
In the case where a filter constant in a filter such as an IIR filter is changed to return the vibration-proof lens to the reference position on the pan or tilt operation, there is a problem that, as the operation depends on the nature of the filter, it is so difficult to control the time and position that the vibration-proof lens cannot be returned to the reference position by intended control.